GaN-Based Solar-Ultraviolet Detection Instrument

Y2O3: Eu3+/PMMA hybrid film as a converter for enhanced harvesting of broadband solar-blind UV light

At present, the most common materials for solar-blind UV light detectors are wide band-gap semiconductors, which generally have high requirements and complex methods for preparation. Ordinary semiconductor materials such as silicon, TiO₂, and Cu₂O were industrialized, but they were excluded for direct harvest of solar-blind UV light due to their inability to absorb solar-blind light photons. Here, inorganic-organic hybrid film of Y₂O₃:Eu³⁺/PMMA was used as a spectral converter to realize the detection of broadband solar-blind UV light by ordinary semiconductor, converting broadband solar-blind UV luminescence to visible luminescence based on down-conversion process, after which the visible luminescence was detected by the Si photo-resister. The results show that hybrid film based on rare earth luminescence materials is particularly valuable for broadband solar-blind UV detection.

Photo-Rheological Fluid-Based Colorimetric Ultraviolet Light Intensity Sensor

This study presents an introduction to a new type of ultraviolet (UV) light intensity sensor using photo-rheological (PR) fluids whose properties, such as color, can be changed by UV light. When the PR fluids were irradiated by UV light, colorimetric transitions were observed. Effectively, this means that their color changed gradually from yellow to red. The degree of the color change depended on the UV light intensity and was characterized by the hue value of the images acquired with a compact image sensor. We demonstrated that UV light-responsive capabilities can be readily imparted to PR fluids, and that the colorimetric responses to different UV light intensities can be used to measure the UV light intensities.

Present Status of III-Nitride Based Photodetectors

This paper describes the characteristics of a variety of AlGaN-based photodetectors (photoconductors, metal-semiconductor-metal photodiodes, Schottky photodiodes and p-i-n photodiodes), grown on sapphire by metalorganic vapor phase epitaxy. The features that determine their performance are analyzed. Results using other substrates (epitaxial lateral overgrown GaN, Si) are also presented.

UV dose measurements of photosensitive dermatosis patients by polycrystalline GaN-based portable self-data-acquisition UV monitors

We have developed a UV monitor with polycrystalline (poly-) gallium nitride (GaN) UV sensors and evaluated its performance from the viewpoint of its effectiveness for use with photosensitive dermatosis patients. The poly-GaN UV sensor is sensitive to UV light from 280 to 410 nm even without optical filters. The UV monitor is a portable self-data-acquisition instrument with a minimum detection level (defined as average UV intensity over 290 to 400 nm) of 2 microW/cm2 and can store UV dose data for 128 days. It allows easy measurement of four orders of magnitude of ambient UV intensity and dose from indoor light to direct solar radiation in summer. Trial use of the UV monitor by five xeroderma pigmentosum patients started in June 2000 and was carried out for 1 year. It was demonstrated that the UV monitor was useful in improving their quality of life.